Signal level adjustment arrangement

Abstract

For signal level adjustment of a multitone signal received over a transmission line ( 1 ) during a training sequence in a DSL system, a programmable high-pass filter ( 2 ) is connected to the transmission line ( 1 ). A programmable gain control unit ( 4 ) is connected between the filter ( 2 ) and an A/D converter ( 5 ). A digital signal processor ( 6 ) is connected with its inputs to the A/D converter ( 5 ), with control outputs ( 7, 9 ) to control inputs ( 8, 10 ) of the filter ( 2 ), and with control outputs ( 11, 13 ) to control inputs ( 12, 14 ) of the gain control unit ( 4 ). The processor ( 6 ) detects signal level differences between the highest and the lowest tone of the multitone signal and programs the filter ( 2 ) to make the signal levels of the highest and the lowest tone equal. The processor ( 6 ) furthermore programs the gain control unit ( 4 ) to adjust its total signal output level to coincide with the dynamic range of the A/D converter ( 5 )

What is claimed is:  
     
       1. An arrangement for signal level adjustment of a multitone signal received over a transmission line during a training sequence in a digital subscriber line system, characterized in that it comprises 
       a programmable high-pass filter ( 2 ) connected with its input terminal to the transmission line ( 1 ),  
       a programmable gain control unit ( 4 ) connected with its input terminal to the output terminal of the high-pass filter ( 2 ), and with its output terminal to an input terminal of an analog-to-digital converter ( 5 ),  
       a digital signal processor ( 6 ) connected with its input terminals to an output bus ( 15 ) of the analog-to-digital converter ( 5 ), with first control output terminals ( 7 ,  9 ) to control input terminals ( 8 ,  10 ) of the high-pass filter ( 2 ), and with second control output terminals ( 11 ,  13 ) to control input terminals ( 12 ,  14 ) of the programmable gain control unit ( 4 ), the digital signal processor ( 6 ) being adapted to detect a signal level difference between the highest and the lowest tone of the multitone signal and in response to the detected difference, program the high-pass filter ( 2 ) via its control input terminals ( 8 ,  10 ) to make the signal level of the highest tone equal to the signal level of the lowest tone, the digital signal processor ( 6 ) furthermore being adapted to program the programmable gain control unit ( 4 ) via its control input terminals ( 12 ,  14 ) to adjust the total signal level on its output terminals to coincide with the dynamic range of the analog-to-digital converter ( 5 ).  
     
     
       2. The arrangement as claimed in  claim 1 , characterized in that the input terminal of the programmable high-pass filter ( 2 ) is connected to the transmission line ( 1 ) via a preamplifier ( 3 ).